Rocker assembly with interconnectable arms

ABSTRACT

A rocker assembly includes a central arm and two outer arms supported on a rocker shaft portion, and a plurality of supporting brackets. The arms, which are actuated by respective cams, actuate at least two lifting valves of a cylinder of an internal combustion engine. Both outer arms may be independently hydraulically coupled by bolt elements to the central arm. Hydraulic ducts extend through the supporting brackets, the rocker shaft portion and the outer arms to communicate with the coupling bolts. The rocker arms, the rocker shaft portion, and the supporting brackets form a pre-assembly unit. The central arm may have a roller on which an associated cam rolls, with the bolt elements of the central arm being arranged coaxially to the roller inside the roller.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a rocker for actuating at least two liftingvalves of an internal-combustion engine with three arms which can beswivelled separately about a common rocker axis and which each have acontact surface for a cam and can be connected by bolt elements whichcan be hydraulically displaced essentially in parallel to the rockeraxis, in the two outer arms, one coupling bolt respectively beingprovided which can be acted upon hydraulically in a separate manner andto which, in each case, a spring-loaded restoring bolt is assigned whichis arranged in the central arm.

From European Patent Document EP 0 259 106 A1, such a rocker is known bymeans of which the lifting valves of an internal-combustion enginecylinder by switching over the bolt elements can be actuated by severalcams. It is an object of the invention to provide additionalimprovements for such a rocker.

This object has been achieved according to the present invention byforming a preassembly unit from the rocker arms, a rocker shaft piece,and two supporting brackets for the rocker shaft piece, and by guidingthe hydraulic ducts by way of the supporting brackets and the rockershaft piece through the outer arms for supplying the coupling bolts.

According to an advantageous further development, the contact surface ofthe central arm may be constructed as a rotatable roller in which thespring-loaded restoring bolts are arranged. In addition, the cam contactsurfaces of the outer arms may be constructed as sliding pads.

This as well as other advantages and characteristics which may besignificant with respect to the invention are explained by means of apreferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a rocker according to a preferredembodiment of the invention;

FIG. 2 is a sectional view similar to FIG. 1;

FIG. 3 is a view of this rocker according to the invention with thesupporting brackets;

FIG. 4 is a sectional view similar to FIG. 1 including the supportingbrackets in a plane representation;

FIG. 5 is the sectional view A--A of FIG. 4;

FIG. 6 is the sectional view B--B of FIG. 4;

FIG. 7a is a perspective view from above;

FIG. 7b is a perspective view from below of another rocker assemblywhich, additionally, has coil spring elements; and

FIGS. 8a, 8b are views of a similar rocker assembly with coil springelements arranged in a different manner.

DETAILED DESCRIPTION OF THE DRAWINGS

Three arms 1, 2, 3 of a rocker or of a rocker assembly, which aredisposed next to one another and can be swivelled about a common axis,actuate two lifting valves of an internal-combustion engine, which arenot shown. As known, these lifting valves are supported by means oftheir shaft ends on hydraulic-play-compensating elements 5 which areinserted into corresponding receiving devices 1', 3' on the free ends ofthe two outer arms 1, 3.

Each arm of the rocker assembly has a contact surface 11, 12, 13 for acam, which is not shown, of a camshaft, which is also not shown. In thiscase, the contact surfaces 11, 13 of the outer arms 1, 3 are constructedas sliding pads, while the contact surface 12 of the central arm isconstructed as a roller which can be rotated about a secondary axis 6.If the individual arms 1, 2, 3 are separated from one another, that is,can be swivelled independently of one another about the rocker axis 4,as a result of the rolling movement of the cams on the contact surfaces11, 12, 13, all arms 1, 2, 3 are swivelled corresponding to therespective cam contour so that, in this case, the respective liftingvalve assigned to the arms 1, 3 is actuated corresponding to therespective cam contour.

However, it is also possible to connect the arm 2 with the arm 1 and/orthe arm 3, that is, to couple the arms 2 and 1 and/or the arms 2 and 3to one another in such a manner that, during a swivel movement of arm 2,arm 1 and/or arm 3 is also taken along. If then the travel course of thecam rolling on the contact surface/roller 12 overlaps the travel coursesof the cams assigned to the contact surfaces 11, 13, during the couplingof the arms 1, 3 to the arm 2, the lifting valves actuated by the arms1, 3 are actuated corresponding to the course of the travel of the camrolling on the roller 12.

The mechanism for coupling the arms 1 and/or 3 to arm 2 is illustratedparticularly in FIGS. 2, 4. As indicated, one coupling bolt 7respectively, which can be longitudinally displaced in the direction ofthe secondary axis 6, is arranged in the arms 1, 3 coaxially withrespect to the secondary axis 6 which extends in parallel to the rockeraxis 4. By way of a hydraulic duct 8, which extends in the respectivearm 1, 3, each coupling bolt 7 can be acted upon on the outer side by ahydraulic medium and, as a result, can be displaced along the secondaryaxis 6. By means of its end situated opposite the hydraulic duct 8, eachcoupling bolt 7 rests on a restoring bolt 9 which, by way of a springelement 10, is supported on a symmetrical partition 14 in the arm 2. Thediameter of each coupling bolt 7 is equal to the diameter of theassigned restoring bolt 9 so that, by being acted upon by hydraulicpressure, the coupling bolt 7 can be pushed partially into the receivingbore 16 for the restoring bolt 9 which is provided in the arm 2.

If therefore the coupling bolt 7 of the arm 1 as well as the couplingbolt 7 of the arm 3 are in the illustrated position in which, amongother things, they are held by means of the respective assignedrestoring bolt 9, the three arms 1, 2, 3 of the rocker assembly areuncoupled from one another and can be swivelled independently of oneanother about the rocker axis 4. In contrast, if, by means of thehydraulic supply acted upon by pressure, by way of the hydraulic duct 8,the coupling bolt 7 of the arm 1 is pressed in the direction of thearrow 15 partially into the receiving bore 16 of the arm 2, the assignedrestoring bolt 9 is also displaced and the spring element 10 iscompressed. As a result, since the coupling bolt 7 is then situated inarm 1 as well as in arm 2, arm 1 is coupled to arm 2 so that the twoarms 1, 2 can only be swivelled together. However, the arm 3 can stillbe swivelled independently and freely in this stage.

However, as an alternative or simultaneously, hydraulic medium, which isacted upon by pressure, may also be supplied by way of the hydraulicduct 8 in the arm 3 so that also the coupling bolt 7 in the arm 3 ispartially pushed into the receiving bore 16 of the arm 2 and in thiscase also displaces the assigned restoring bolt 9 and compresses theassigned spring element 10. As an alternative or in addition, the arm 3is in this case also coupled to the arm 2. With the release of thehydraulic pressure in the hydraulic ducts 8 in the arm 1 and/or the arm3, this coupled connection is released again because then, under theeffect of the respective spring element 10, the respective restoringbolt 9 will push the respective coupling bolt 7 back into the respectivearm 1, 3 into the illustrated position.

By means of the shown rocker assembly, it is therefore not only possibleto either actuate the arms 1, 3 independently of one another or tocouple only the arm 1 or only the arm 3 or both arms 1, 3 to arm 2, but,in addition, this rocker assembly is distinguished by an extremelycompact construction. On the one hand, this extremely compactconstruction is achieved in that bolt elements, specifically the tworestoring bolts 9 including the assigned spring elements 10, areessentially arranged inside the roller 12. On the other hand, it is alsorecognized that it is sufficient to construct only the contact surface12 of the arm 2 as a roller while sliding pads are sufficient for thecontact surfaces 11, 13 of the arms 1, 3.

As explained above, the travel course of the cam assigned to the arm 2overlaps with the travel courses of the cams assigned to the arms 1, 3.Therefore, the cam of the arm 2, particularly in the high rotationalspeed range of the internal-combustion engine, must actuate the liftingvalves which are not shown, while, in the low rotational speed range ofthe internal-combustion engine, the cams assigned to the arms 1, 3actuate the lifting valves. Since the arms 1, 3 are coupled to the arm 2preferably at the higher rotational speeds of the internal-combustionengine, as explained in the following, this coupling can definitely takeplace in steps. Significant valve actuating forces on the contactsurface/roller 12 also only take place at these higher rotational speedsof the internal-combustion engine. As desired, the roller therefore actshere as an element which reduces the frictional losses. In contrast, inthe case of low rotational speeds of the internal-combustion engine, thefrictional losses between a cam and the contact surface 11, 13 of theassigned rocker arm 1, 3 are relatively low anyhow. However, since thesecontact surfaces 11, 13 become operative only at low rotational speedsof the internal-combustion engine within the scope of the actuating ofthe valves, no rollers are required for these contact surfaces 11, 13and sliding pads are completely sufficient.

As indicated above, the coupling of the arms 1, 3 to arm 2 make takeplace in steps. In this case, the circuit logic permits a combination ofa valve switch-off, a partial travel and a full valve travel. When thearm 1 is uncoupled from the assembly, the pertaining valve isessentially switched off. However, in order to prevent an accumulationof fuel in front of the lifting valve, it is required to open this valveby a minimal amount which is caused by a corresponding cam acting uponthe narrow contact surface 11 of the arm 1. When the arm 3 is uncoupled,the valve assigned to this arm carries out a partial lift by means ofthe assigned cam which acts upon the wider contact surface 13. In thiscase, in a lower rotational speed and load range of theinternal-combustion engine, both arms are uncoupled so that the firstlifting valve is essentially (this is, with the exception of the minimalopening lift) switched off and the second internal-combustion enginevalve carries out a partial lift. In a medium rotational speed and loadrange of the internal-combustion engine, the arm 3 is coupled to the arm2 so that now, because of the effect of the cam assigned to the arm 2 onthe roller 12, the second valve carries out a full lift, while the firstinternal-combustion engine valve remains switched off. In addition, inan upper rotational speed and load range of the internal-combustionengine, the arm 1 is coupled to the arm 2 so that now the twointernal-combustion engine valves will carry out a full liftcorresponding to the cam acting upon the roller 12.

The arms 1, 2, 3 form a preassembly unit together with a rocker shaftportion 17, on which the three arms 1, 2, 3 of the rocker assembly aredisposed, as well as together with the two supporting brackets 18 forthe rocker shaft portion 17. By way of the supporting brackets 18, thispreassembly unit, as a separate subassembly, can simply be screwed to acylinder head 19 of an internal-combustion engine which is shown only asa fragment. For this purpose, a retaining clip may be provided whichprevents that this subassembly will fall apart during assembly work.This retaining clip may also be removable.

Within this rocker assembly, the hydraulic ducts 8 in the arms 1, 3 aresupplied with hydraulic medium by way of hydraulic ducts 20, 22 in theshaft portion 17 or in the bearing bracket 18. Naturally, it is requiredto provide for each arm 1, 3 a separate hydraulic duct 20 as well as aseparate hydraulic duct 22 if it is to be possible, as explained above,to couple each of these arms 1, 3 separately to the arm 2. For thisreason, the two hydraulic ducts 20 are constructed in the rocker shaftportion 17 as separate branch ducts which are apart from one another.Each of the two branch ducts or hydraulic ducts 20 is supplied withhydraulic medium by way of the supporting bracket 18 adjoining it or byway of the hydraulic duct 22 provided therein. In this case, thehydraulic ducts 20 of the supporting brackets 18 are connected withdifferent supply ducts 21, 23 which extend essentially side by side inthe cylinder head 19 of the internal-combustion engine, as illustratedin FIGS. 5, 6. The supporting bracket 18 which is adjacent to the arm 1is connected by means of its hydraulic duct 22 to the supply duct 21,while the supporting bracket 18 adjacent to the arm 3 is connected bymeans of its hydraulic duct 22 to the supply duct 23.

The embodiments according to FIGS. 7a, 7b, 8a, 8b also show coil springelements 24, 25 which are guided through the sections of the arms 1, 2,3 concentrically to the rocker axis 4. In both embodiments, one end ofthe coil spring elements 24, 25 is supported on the rocker arm 2. In theembodiment according to FIGS. 7a, 7b, the other end of the coil springelements 24, 25 is supported on the other, respectively adjacent rockerarm 1 or 3. In the embodiment according to FIGS. 8a, 8b, the other endof the coil spring elements 24, 25 is, in each case, supported on theadjacent supporting bracket 18.

It is a significant purpose of these coil spring elements 24, 25 topress the rocker arm 2 against the cam assigned to this arm 2 when thisarm 2 is not coupled to one of the two other arms 1, 3. These coilspring elements 24, 25 are therefore used particularly for the precisepositioning of the rocker arm 2. In the embodiment according to FIGS.8a, 8b, these two coil spring elements 24, 25 also hold the rockerassembly together so that the latter may be constructed as a preassemblyunit.

Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is by way of illustration andexample, and is not to be taken by way of limitation. The spirit andscope of the present invention are to be limited only by the terms ofthe appended claims.

We claim:
 1. A rocker assembly for actuating at least two lifting valvesof an internal-combustion engine comprising:a plurality of rocker armswhich can each be swivelled independently about a rocker shaft portionhaving a rocker axis, said rocker arms each having a contact surface fora cam, said rocker arms comprising a central arm and two outer arms; acoupling bolt arranged in each of said two outer arms, said couplingbolts being hydraulically displaceable in a direction essentiallyparallel to said rocker axis to interconnect a respective said outer armwith said central arm; a spring-loaded restoring bolt corresponding toeach said coupling bolt, said spring-loaded restoring bolts beingarranged in said central arm; and a plurality of supporting bracketsconfigured to support at least one of said rocker shaft portion and saidrocker arms wherein hydraulic ducts extend through said supportingbrackets said rocker shaft portion and said outer arms to communicatewith said coupling bolt, and wherein said rocker arms, said rocker shaftportion and said supporting brackets form a preassembly unit.
 2. Arocker assembly according to claim 1, wherein the contact surface of thecentral arm is constructed as a rotatable roller.
 3. A rocker assemblyaccording to claim 2, wherein the spring-loaded restoring bolts arearranged coaxially within the roller.
 4. A rocker assembly according toclaim 1, wherein at least one coil spring element is arrangedessentially coaxially with respect to the rocker axis, is supported at afirst end on the central arm, is supported at a second end on one of theouter arms, and is configured to bias the central arm against the camassigned thereto.
 5. A rocker assembly according to claim 1, wherein thecam contact surfaces of the outer arms are constructed as sliding pads.6. A rocker assembly according to claim 1, wherein at least one coilspring element is arranged essentially coaxially with respect to therocker axis, is supported at a first end on the central arm, issupported at a second end on one of the supporting brackets, and isconfigured to bias the central arm against the cam assigned thereto. 7.A rocker assembly according to claim 1, wherein said hydraulic ductscommunicate said coupling bolts with at least one hydraulic pressuresource for hydraulic displacement of said coupling bolts.
 8. A rockerassembly according to claim 7, wherein one of said coupling bolts iscommunicated with a first of said hydraulic pressure sources, andwherein the other of said coupling bolts is communicated with a secondof said hydraulic pressure sources.
 9. A rocker assembly according toclaim 1, wherein a first of the supporting brackets is arranged at oneaxial end of said rocker shaft portion, and a second of the supportingbrackets is arranged at the other axial end of said rocker shaftportion.
 10. A rocker assembly according to claim 9, wherein said firstand second supporting brackets are arranged outside of said plurality ofrocker arms in an axial direction with respect to said rocker shaftportion.
 11. A rocker assembly according to claim 9, wherein each ofsaid rocker arms includes a rocker shaft engaging portion whichswivellably engages said rocker shaft portion, said first of thesupporting brackets being arranged adjacent and axially outside of saidrocker shaft engaging portion of one of said outer arms, and said secondof the supporting brackets being arranged adjacent and axially outsideof said rocker shaft engaging portion of the other of said outer arms.12. A rocker assembly formed as a preassembly unit which is attachableas a subassembly to a cylinder head of an internal-combustion engine,comprising:a rocker shaft portion defining a rocker axis and having afirst axial end and a second axial end; a first supporting bracketsupporting said first axial end of the rocker shaft portion; a secondsupporting bracket supporting said second axial end of the rocker shaftportion; a plurality of rocker arms arranged on said rocker shaftportion between said first supporting bracket and said second supportingbracket, each of said rocker arms being independently swivellable aboutthe rocker shaft portion, said rocker arms each having a contact surfacefor a cam, said rocker arms comprising a central arm and two outer arms;a coupling bolt arranged in each of said two outer arms, said couplingbolts being hydraulically displaceable in a direction essentiallyparallel to said rocker axis to interconnect a respective said outer armwith said central arm; and a spring-loaded restoring bolt correspondingto each said coupling bolt, said spring-loaded restoring bolts beingarranged in said central arm, wherein at least one hydraulic pressuresource is communicated with said coupling bolts via hydraulic ductswhich extend through said supporting brackets, said rocker shaft portionand said outer arms, in order to selectively displace said couplingbolts to interconnect said arms.
 13. A rocker assembly according toclaim 12, wherein a first hydraulic pressure source is communicated withone of said coupling bolts via a first set of hydraulic ducts whichextend through a respective one of said supporting brackets, said rockershaft portion, and a respective one of said outer arms, and wherein asecond hydraulic pressure source is communicated with the other of saidcoupling bolts via a second set of hydraulic ducts which extend throughthe other of said supporting brackets, said rocker shaft portion and theother of said outer arms, said first set of hydraulic ducts beingseparate from said second set of hydraulic ducts.